extract database config into new file

- this will be used in the future to allow environment-specific database 
configurations
- functional no-op in prod

Author: dfarrow0

src/server/api_helpers.php

@@ -1,9 +1,12 @@
 <?php
+// load database connection parameters
+require_once(__DIR__ . '/database_config.php');
 
 // connects to the database
 function database_connect() {
-  $host = 'localhost';
-  $port = 3306;
+  global $DATABASE_CONFIG;
+  $host = $DATABASE_CONFIG['host'];
+  $port = $DATABASE_CONFIG['port'];
   $username = Secrets::$db['epi'][0];
   $password = Secrets::$db['epi'][1];
   $database = 'epidata';
@@ -260,4 +263,4 @@ function record_analytics($source, $data) {
 }
 
 
-?>
+?>

src/server/database_config.php

@@ -0,0 +1,7 @@
+<?php
+// production database connection parameters
+$DATABASE_CONFIG = array(
+  'host' => 'localhost',
+  'port' => 3306,
+);
+?>